An American pilot and his Nigerian officer were killed along with four passengers when a helicopter plunged into a lagoon in Nigeria's financial hub Lagos, the US-based operator said on Thursday.
The twin-engine Sikorsky 76C+, operated by the Bristow Group, was heading from an offshore oil rig to the international airport when it plunged into the water in the north of the city on Wednesday.
Four bodies were recovered soon after and six people treated in Lagos hospitals, while the bodies of two more victims were discovered on Thursday, according to the National Emergency Management Agency (NEMA).
Among the dead was the two-man crew -- Captain Jay Wyatt, of Oklahoma, and First Officer Peter Bello, of Nigeria -- Bristow said in a statement.
Witnesses reported hearing a loud bang before the helicopter nose-dived into the water near the 12-kilometre (seven-mile) Third Mainland Bridge, the longest of three bridges connecting Lagos Island to the mainland.
The nationalities of the passengers have not been revealed but the Vanguard national daily newspaper named the six survivors as Nigerians.
Wyatt had been with Bristow since 2006 while Bello joined in 2014, the company said in a statement describing the pair as "experienced and qualified".
"We are shaken and deeply saddened by this tragic accident. Our thoughts and prayers go out to the families, friends and loved ones of all those on board," said Bristow Africa director Duncan Moore.
- 'Heartbreaking' -
Wyatt started his career as an avionics technician with the United States Navy in 1997, according to his LinkedIn profile, before moving into security, installing and upgrading alarm systems in US embassies as part of a contract with the State Department.
He spent two years as a flight instructor with Bristow's training academy in Florida before becoming a pilot based in Port Harcourt, southern Nigeria in 2008.
Nigerian RnB artist Banky-W paid tribute to Bello, posting a picture of the pilot on the Instagram photo-sharing social media platform.
"So sad.. so sad... death is so painful, unfair and final. RIP to Peter Bello and all the victims of the Bristol Helicopter Crash," the 34-year-old singer, real name Olubankole Wellington, wrote.
"May God be with all their families and friends in these heartbreaking times."
Texas-based Bristow's fleet of around 500 helicopters services the global energy industry and it has transportation operations in Nigeria and most other major offshore oil and gas producing regions of the world.
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Sikorsky says its S-76 range has built up an "outstanding and enviable" record for safety and reliability over 30 years of improvement and six million hours in flight.
Before the Lagos accident the model had been involved in just two crashes with multiple fatalities since 2000, in 2002 and 2005.
There have been several military helicopter accidents across Nigeria in recent years, but air crashes involving private choppers have been relatively rare.